HD Pentax-DA 21mm F3.2 Limited

Aberrations

On this page, we will examine how the DA 21mm Limited controls various types of aberrations and artifacts.

Flare

The DA 21mm Limited showed good resistance to flare and ghosting. According to Ricoh, the new HD coating "Enables the reduction of flare and ghosting for the shooting of clear, high-contrast images even under backlighting and other adverse conditions." As Pentax shooters already know, the previous SMC coatings were as good as any in the industry, so the previous bar is set high.

In our PentaxForums review of the new Limited lenses, we did determine a small advantage to the HD coatings for flare. See our in-depth review of HD versus SMC coatings here.

In images with very bright objects in the frame, the DA 21mm Limited showed very little veiling glare. The scene below, with the sun in the corner of the frame, maintains a high level of contrast along the left and right sides of the photo.

Low veiling glare/good contrast in extreme settings. (Click to enlarge.)
K-5 IIs, 1/80s, f/8, ISO 400

As in the above image, the DA 21mm Limited did show flare in the immediate vicinity of the bright object itself. For the most part the flare was contained around the bright source, but there was a spot of flare separated from the source, as shown in the photo below. Note the green spot in the distant hillside.

Green spot reflected from the light source. (Click for larger.)
K-5 IIs, 1/2500s, f/11, ISO 200

Or course, this kind of flare can be used to artistic effect for those so inclined. Given the small size of the DA 21mm Limited's front element, it is fairly easy to shield the lens from sharp light sources.

In our previous comparison of the HD to SMC versions of the Limited lenses, the HD version did show a small improvement over the already-excellent SMC coatings. 

Shape of Flare

One of the key differences between the SMC and HD versions of the lens is the shape of the aperture blades. The SMC Limited lenses produce sharp starburst shapes due to straight aperture blades, but the HD versions do not.

It isn't until about F8 that the aperture blades have enough of an edge to create any kind of starbust at all. Even at F11, the shape of the flare isn't as regularly geometric as the SMC version.

At F4, lights show no geometric shape. (Click to enlarge.)
K-5 IIs, 1/2s, f/4, ISO 800

Chromatic Aberration

In our field testing, the DA 21mm Limited did exhibit a small amount of both red/green chromatic aberration and sensor blooming.

The red/green chromatic aberration at the image periphery was mild, but present, at most apertures. It was not noticeable in low contrast settings. For a wide angle lens, the results were decent. Stopping down didn't resolve the aberrations, as in the following scene shot at F11.

Full image showing red/green chromatic aberration at edges. (Click to enlarge.)
K-5 IIs, 1/30s, f/11, ISO 800

The crops below show a simple fix available in post-processing. This is a simple check box in many post-processing tools, so the red/green chromatic aberrations are not difficult to resolve. Notice too that the corrected image shows much better edge sharpness.

In the edges, the DA 21mm Limited does show some sensor blooming in very high contrast subjects, most noticeable at F3.2. While this is also easily addressed in many post-processing tools, it can be more difficult than red/green aberrations mentioned above if the subject has similar colors to the blooming.

The DA 21mm Limited showed almost no longitudinal chromatic aberration (also called axial color), where the out-of-focus blur shows magenta or green fringing. The relatively slow F3.2 aperture surely helps in this regard.

Verdict

The DA 21mm Limited shows an excellent resistance to veiling glare, keeping a high level of contrast even with strong light sources in the frame. Flare overall is well controlled, with only an occasional ghosted green spot appearing counter to a strong light source.

The level of red/green chromatic aberrations in high contrast edges is present but mild and easily corrected. Likewise, there is some sensor blooming in the corners of very high contrast subjects, most pronounced wide open. The lens showed virtually no axial color in the out-of-focus areas.

Compared to other wide angle lenses, the DA 21mm Limited performs well overall for aberrations. The biggest criticism is from those looking for geometric starbursts as produced by the SMC version.